1. Technical Field
The present invention relates generally to video decoders having complexity reduction systems, and more particularly to a post processing system and method for reducing the pulsing of video sharpness caused by complexity reduction.
2. Related Art
As the demand for feature-rich video processing applications continues to increase, the need to manage computational resources associated with such applications has become an ongoing challenge. One example of a system that manages video resources is a reduced complexity decoding system. In such a system, the decoder complexity can be reduced significantly using in-loop processing techniques. For instance, well-designed discrete cosine transform (DCT) masking can simplify the inverse DCT (IDCT) process, delivering gracefully degraded video quality and reducing decoding complexity.
In addition, embedded resizing, a scheme that incorporates the scaling function within the decoding loop, achieves complexity and memory savings from reduced resolution IDCT and motion compensation. Present complexity reduction systems can reduce CPU cycles by 30 percent while delivering satisfactory video quality for most normal scene sequences.
As is known, the trade-off for complexity reduction is an introduction of decoder errors into the decoding loop. Specifically, errors will propagate via motion compensation until the next Intra-coded or “I” frame. As a result, the video quality usually degrades progressively within a Group of Pictures (GOP), resulting in a prediction drift.
Since the most common degradation is loss of sharpness, typical prediction drift is seen by a viewer as a pulsing of video sharpness, i.e., the periodic occurrence of some gradually burring pictures followed by a sharp picture. Although some techniques help to reduce the prediction drift, such as frame-type-dependent processing which provides protection to those pictures contributing to predictions, the techniques cannot eliminate the drift problem. As long as there are errors in the prediction path, there will be prediction drift.
Accordingly, improved techniques are required to better address prediction drift in complexity reduced decoding systems.